Method for tensioning sieves



Nov. 22, 1966 N. J. Bol-1R 3,286,338

METHOD FOR TENSIONING SIEVES Filed Feb. 4, 1964 5 Sheets-Sheet l 39k 40 9 FIG. l

Ff (33 34 #ik \\\f 36 Hll( 53 42 @Il 48 55 E\ I rlrhmi .yi ll'll 27 C54 f i l I r 5w l' i :I /|5 l s *e l l 12/ i s V- -`-``m l l l I I i lllnhl i r 2j L INVENTOR. NICHOLAS J. BOHR y? yay ATTQRNEYS Nov. 22, 196e N. J. BGHR 3,286,338

METHOD FOR TENSIONING SIEVES Filed Feb. 4, 1964 s sheets-sheets 7W FIG. 2 f8 INVE1 T R. 66 NICHOLAS J. BEFCIDR ATTORNEYS N. J. BOHR METHOD FOR TENSIONING SIEVES Nov. 22, 1966 5 Sheets-Sheet 5 Filed Feb. 4, 1964 INVENTOR. NICHOLAS J. BOHR FIG? ATTORNEYS United States Patent O 3,286,338 METHOD FOR TENSIONING SIEVES Nicholas J. Bohr, 20451 Tracy Ave., Euclid, Ohio Filed Feb. 4, 1964, Ser. No. 342,408 3 Claims. (Cl. 29-446) This invention concerns a novel method for tensioning presoldered woven wire cloth sieves such as covered by the approved standards of the American Standards Association A.S.A. No. Z2l3.ll95 8, the American Association State Highway Official Standard A.A.S.H.O. No. M92-42 and the American Society for Testing Materials designation E11-61.

The presoldered woven wire cloth sieves to be tenlsioned by the method of this invention are typically constructed from wire cloth of brass, bronze, or other suitable wire whic-h is not coated or plated. The average opening between the adjacent warp land the adjacent shoot wires is closely controlled within permissi-ble variations according to the standard specifications which will in general vary from the average opening plus or minus 2 to 7 percent depending upon the sieve size and the wire diameter.

The method of the present invention has Ibeen specifically devised to provide efficient tensioning of presoldered woven -wire cloth sieves so that undesirable opening distortion, looseness and waviness in the cloth may be positively minimized during mass production of the sieves.

The woven wire cloth sieves to be tensioned by the method of the instant invention have the wire cloth soldered to the frame by means of a smoothly filled joint or fillet which prevents the material being sieved from catching in the joint Ibetween the cloth and the frame. The frames are generally annular and olf brass and contain a lower annular skirt portion which holds the cloth to the upper member or frame by means of the soldered joint therebetween.

The .problem in the art of looseness, waviness and distortion of the wire cloth openings has been the natural result of theinitial assemblying of the upper frame and the wire with the lower sieve skirt member. This results from the fact that during the assembly and bonding or soldering operation, it is impossible to obt-ain uniform tension throughout the surface of the wire cloth,

In one prior art procedure for tensioning presoldered woven wire cloth sieves, the skirt is placed over a mandrel and the flange is tapped with a wooden mallet at a plurality of arbitrarily selected points around the periphery. This has resulted in poor quality control of the sieves and has required skilled labor in order to produce sieves which comply with the stand-ard specifications.

Accordingly, it will be understood that the present invention relates to the final tensioning of the woven wire cloth by means of a novel method specifically designed to produce an accurate and quality sieve of uniform wire cloth tension.

Broadly, the method of tensioning the presoldefre-d woven wire cloth sieve comprises providing a preassembled sieve structure having an upper annular fra-me with outwardly and downwardly turned flange portions on its lower margin and a concentric lower annular skirt having an outwardly and upwardly angled Iflange portion on its upper margin nested in the angle formed by the flange porti-ons of the upper frame with an annular piece of wire cloth held therebetween by means of a filleted solder joint. The 4thus preass-embled and presoldered woven wire cloth sieve structure is then tensioned by simultaneously exerting a downwardly and radially inwardly directed force about substantially all of the periphery of the flange of the upper frame uniformly to increase the tension on the cloth.

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In its more specific aspects, the method contemplates the use of the step of inserting the lower skirt of the preassernble'd structure on a mandrel prior to the step of exerting the tensioning force.

The apparatus Ifor performing the novel method of tensioning the presoldered woven wire cloth sieves includes dies segments which have downwardly and inwardly facing angular metal forming surfaces. These die segments are mounted upon a guide plate for radial movement. Means are provided for moving the guide plate in a Vertical path such that the die segments come into engagement with fixed cam means located -above them upon upward movement of the guide plate. The engagement of the die segments with the fixed cam means causes radial inward movement of the die segments in a radial direction upon the guide plate. A mandrel means is mounted within an open central portion of the guide plate such that the presoldered fianged wire cloth sieve may be placed on the mandrel means. Thus, when the guide plate is moved upwardly to engage the segments with the fixed cam means, `the radially inwardly moving segments come into engagement with the sieve flange only to deform the flange downwardly about the periphery of the sieve. This action uniformly tensions the presoldered woven wire cloth to .provide a sieve structure having a minimum of opening distortion, looseness and waviness.

With the brief description of the invention and the problems of the prior art in mind, it is an object of the invention to provide an improved method of tensioning presoldered woven wire cloth sieves by simultaneously exerting a downwardly and radially directed inward force about substantially all of the periphery of the upper flange to tension uniformly the wire clot-h to provide .a sieve structure having a minimum of opening distortion, looseness and waviness.

Other and more specific -objects of the invention will be apparent from the detailed description to follow.

In the drawings:

FIG. 1 illustrates an elevational view with portions broken away for clarity of one embodiment of the apparatus for tensioning presoldered woven wire cloth sieves according t-o the invention.

FIG. 2 is a cross sectional view of the apparatus along the line 2 2 of FIG. 1.

FIG. 3 is an enlarged view similar to FIG. 2 of a fragmentary portion of the apparatus.

FlG. 4 is an exploded view of the components of a woven wire cloth sieve of .the type to be tensioned by the method of the instant application.

FIG. 5 is a schematic cross sectional elevational View illustrating a portion of the support frame and components of the apparatus of FIG. l with a presoldered woven wire sieve m-ounted thereon.

FIG 6 is a view similar to FIG. 5 during radial movement of the die segments.

FIG. 7 is a View similar to FIGS. 5 and 6 illustrating the relative location of certain of the elements and the sieve at the completion of the tensioning of the woven wire cloth.

FIG. l illustrates an apparatus for tensioning presoldered woven wire cloth sieves in which a support frame 1 has a fixed base plate 2 mounted on suitable structural members 3 and 4. The fixed base plate 2 is generally square or rectangular in shape and has in the marginal areas adjacent its corners four upstanding vertical post members 5, 6, 7 and 8. These post members together with a fixed top plate 9 and a moveably mounted intermediate base plate 10 are supported on the posts 5, 6, 7 and 8 to make up the complete support frame 1.

Mounted on the fixed =base plate 2 and controlling the vertical position of the base plate 10 is a hydraulic element generally designated by the numeral 12 having appropriate inlet 13 and outlet 14 which lead to a suitable manual hydraulic pump or other `source of controlled hydraulic pressure (not shown) of a type well known in the art. The hydraulic actuating device has an outer cylindrical casing 15 and a piston 17 having an exposed end. The piston 17 is actuated by the variations of hydraulic pressure within the cylindrical casing 15. A collar 18 is welded or otherwise suitably secured to the bottom of the base plate 10 such that the upper end of the exposed portion of the piston 17 of the hydraulic device 12 may be seated therein for force transmission to the base plate 10.

The base plate 10 is moveably mounted on the posts S, 6, 7 and S by means of apertures, such as aperture 24 in register concentrically with the four vertical posts,

Within the aperture 24 of the base plate 10 is a bushing member 25 having a fiange 26 which supports the marginal area 27 of the base plate 10 and maintains the proper alignment of the plate 10 during movement along the vertical support posts of the frame 1. The upper end of the bushing 25 extends above the base plate 10 and is externally threaded to receive a suitable nut 2S to hold the bushing in place with the base 10.

Identical structure is found at each of the four corners of the base plate 10 to provide smooth bearing surfaces for the base 10 on the vertical posts during its movement upwardly or downwardly in response to the hydraulic cylinder or actuating mechanism 12.

The fixed top plate 9 has attached thereto, above the base plate 10 on the lower side of the fixed top plate 9, a generally cylindrical xed cam member 3b having an inwardly and upwardly angled camm-ing surface 32 thereon. The fixed camming member is attached to the fixed top plate by means of suitable countersunk bolts 33v being threadedly engaged therewith. The fixed top plate 9 is held in position on posts 5, `6, 7 an-d 8 'by means of `bores such as the bore 34 through which the reduced diameter extension 35 at the uppermost end of the post 5 passes. The reduced diameter portion 35 of the post 5 provides a shoulder 36 upon which the fixed top plate 9 is seated. Suitable threads 39 are provided on the end of the fixed post such that a nut 40 may secure the fixed top plate `9 tightly against a shoulder 36.

Mounted between the face of the fixed top plate 9 and the uppermost surface of the collar 25 is a spring 42 which normally urges the base plate and the piston 17 downwardly away from the fixed camming member 30. The structure at each of the corners 9 is similar to that described with respect to the structure adjacent the fixed vertical post 5 such that the vertical posts 6, 7 and 8 support the other corners of the fixed top plate 9 in the same manner.

Coaxially aligned with the cylindrical fixed camming member 30 mounted on the top surface of the moveable base plate 10 is a mandrel means 45. Suitable means such as bolts 46 are provided to secure the mandrel means to the -base plate 1d. The mandrel 45 has a reduced cylindrical portion 47 at its uppermost end which provides an annular shoulder 48 thereon which terminates at its outermost end in the lower outer cylindrical wall 49 of the mandrel 45.

An annular guide plate 50 is provided about the periphery of the mandrel surface 49 but is of somewhat less thickness than the cylindrical height of the surface 47 such that it may be spaced from the top surface of the Ybase plate 10. Accordingly, the annular guide plate 5t) may be spaced from the base plate 10 while the top sur face 51 of the guide plate 5t) is fiush with the `shoulder `48 of the mandrel. The guide plate 50 is maintained in this position by means of a series of bolts 53 hav-ing springs 54 mounted on the-Shanks thereof between the plates 10 and 50. The bolts 53 pass through suitable counterbored openings 5S in the guide plate such that the downwardly opening counterbores 56 receive the upper end of the springs 54. The bolts 53 are threadedly secured in suitable holes 57 in the upper surface of the base plate 10.

As illustrated in FIG. 2, for instance, a plurality of die segments 60 are prov-ided about the periphery and spaced from the periphery of the mandrel 45. As illustrated, three dies are used although it should 'be understood that any number of dies Imay be used if so desired.

As seen in FIGS. 5-7, the die segments 64) have a workpiece flange forming surface 62 which is angled radially inwardly and upwardly with respect to the base plate 10. The segments taken together in their deforming position define a substantially annular face 63 which is bevelled as at 64 Ebetween the front face 63 and a top annular surface `65 formed by the segments. Between the outer annular surface 66 of the segments and the top surface 65 is the bevelled cam engaging surface 68 which is in spaced opposing relationship to the camming surface 32 of the fixed die 30 and directly below the same before the actuation of the hydraulic mechanism 12.

The die segments 60 are mounted between angular slide members 69 which have an undercut portion for yco-operation with a laterally depending ange 70 on the die segments 6l) to retain the die segments against vertical movement independent of the guide plate 50. Also within the top surface of the guide plate 50 :radially spaced by an amount equal to n/ 360, where n is the number of die segments, are radial channels 72. Extending from a seat 73 in the die segments 60 and held therein by means of set screws 74 threadedly associated with the outer surface 66 by bores 75 in the outer surface of the die segments 60 are guide keys 77. As shown in FIG. 5, each key 77 is dimensioned so as to extend downwardly to the base of its respective guide slot '72 in the guide plate 50. The key 77, as shown, is freely longitudinally slideable along said guide slot in a radial direction against the 'bias of a spring 78 `disposed in the radial guide slot 72 in abutting `relationship with the guide key 77 and the radially innermost end 79 of the slot 72.

The woven Wire cloth sieve to be tensioned according to t'he principles lof this invention, on the illustrated atpparatus is initially formed from 1an upper frame member 80 as shown in FIG. 4. The frame 80 has a substantially vertical annular wall with an outwardly Iturned bead 82 at its uppermost marginal edge and :a generally horizontally outwardly extending flange portion 83 which terminates in a generally downwardly and radially outwardly extending flange portion 84. A woven wire cloth blank of generally circular shape is provided having sufficient radius Ito extend slightly beyond the endmost flange portion 84 of the annular upper fname 80. The cloth 85 in the assembled sieve is held in the angle formed by the flange portion 83 and the ange portion 84 by means of a lower annular skirt 86 having an outwardly and upwardly'turned flange portion 87 which has its upper end 88 Iof a diameter slightly less than rthe diameter of the `circle defined by the apex of the angle between the portions 83 and 84. The cloth 85 is clamped and held around the e'dlge 88 yby a radially inwand defonmation lof the flange portion 84 under the lower skirt flange 87. The integrity of 'this arrangement is then maintained by a soldering operation and the sieve is then in the condition illustrated in FIGURES 5 and 6, ready to be tensioned.

The tensioning method as performed on the illustrated apparatus is set fontlh in FIGURES 5, 6 and 7.

Initially, the presoldered woven wire cloth sieve is placed on the mandrel 45 with .the lower annular skirt 86 surrounding the reduced portion lof the mandrel 47 and resting on the shoulder 48.

Upon actuation of the hydraulic mechanism 12, the piston 17 laots to move the base platte 10 and Ithe die segments thereon upwardly until they 'assume a position with the surface 68 in engagement with the fixed camiming surface 32 as shown in dotted lines in FIGURE 5. It will be seen that the springs 54 aire of suicient strength tto maintain the maximum separation between the plates 10 and 5t? as they continue their vertical movement as seen in FIGURE 6, with the surfaces 68 and 32 acting to radially inwardly cam the die segments 60` against the outwardly biasing force of the spring 72 until the forming surface 62 comes in register with the outside of the angled portion of the upper frame 80 at a position slightly above the flan-ge portions 83 and 84.

At this point in the radial movement of .the die segments 60 the surface 68 of the segments clears the radially inwardmost point of the xed camming surface 32 and the die segments and movable structure including the workpiece mounted on the mandrel shoulder 48 continue their vertical upward movement until the top surface 65 of the die segments engage t-he llower inner surface 90 of the fixed cam means 30. Almost simultaneously with rthis occurrence the forming surface 62 of the segments engages the outside lof the angled portion of the upper lirame 80. The hydraulic piston 17 continuing upward to drive the plate 10 with the ldie segments 60 and the guide plate 50 .being positively stopped by the surface 90 of the fixed structure, relative movement occurs lbetween the base plate 10 and mandrel `4S in the die segments 60 for the first time in a vertical direction. This vertical movement is translated through .the forming surface 62 to the bead formed by the sieve flange portions such that the lower ange portion 84 is curled further under the Han-ge portion 88 of the skirt while the flange portion 83 is driven down even further out of its initial substantially horizontal orientation.

In elfect then, the wire cloth is further tensioned because itis drawn radially and downwardly a great distance throughout substantially all lof its 360 periphery. During this relative movement the reaction force to the forming force exerted by the forming surface `62 is supplied by the mandrel shoulder 4S while the spring 54 insures lohat the full eifec-t of the hydraulic forces ot the actuator 12 are not transmitted to the sieve structure in a manner which would damage it.

Moreover, it will be noticed that there is no positive radial clamping of the workpiece which would damage its polished brass linish.

Accordingly, it will be seen that an eicient method for tensioning pre-soldered woven wire screen cloth has been provided Iby the instant invention.

For ease of description the principles of the invention have been set forth in connection with but a single illustrated embodiment. It is not my intention that the illustrated embodiment nor the terminology employed in describing it be limiting inasmuch as variations in these may be made without departing from the spirit of the invention. Ratlher, I desire to lbe restricted only by the scope of the appended claims.

I claim:

1. A method of tensioning presoldered woven wire cloth sieves comprising:

providing a preassemlble-d sieve structure having an upper annular frame with outwardly and downwardly turned flange portions on its lower margin and a concentric lower annular skirt having an outwardly and upwardly angled flange portion on its upper margin nested in the angle formed by the flange portions of said upper frame 'with Yan annular piece of wire cloth held therebetween by means of flleted solder,

simultaneously exerting a downwardly and radially directed inward force about substantially all of the periphery of .the flange of the upper frame uniformly to deform said angled flange on said lower skirt downwardly and radially outwardly and said turned flange on said upper annular frame downwardly and radially inwardly about the edge of said radially outwardly deformed flange on said skirt to thereby increase the tension on said cloth.

2. The method of claim 1 which includes the step of inserting the lower skirt of the preassembled sieve structure on a mandrel prior to the step of exerting a torce.

3. The method of claim 1 in which prior .to the step of simultaneously exerting a downwardly and radially directed inward force, the step of placing the lower edge of the lower skirt against a shoulder of lthe lower end of the sieve holding mandrel is included.

References Cited bythe Examiner UNITED STATES PATENTS 181,262 8/ 1876 Herring 209-403 221,322 ll/ 1879 Kennedy 209-403 502,044 7 1893 Lindemann 29-5 11 1,167,927 1/1916 Pfalzgraf 209-403 2,507,578 l/ 1950 Schelperoort. 2,654,940 10/ 1953 Law.

CHARLIE T. MOON, Primary Examiner. 

1. A METHOD OF TENSIONING PRESOLDERED WOVEN WIRE CLOTH SIEVES COMPRISING: PROVIDING A PREASSEMBLED SIEVE STRUCTURE HAVING AN APPER ANNULAR FRAME WITH OUTWARDLY AND DOWNWARDLY TURNED FLANGE PORTIONS ON ITS LOWER MARGIN AND A CONCENTRIC LOWER ANNULAR SKIRT HAVING AN OUTWARDLY AND UPWARDLY ANGLED FLANGE PORTION ON ITS UPPER MARGIN NESTED IN THE ANGLE FORMED HY TEH FLANGE PORTIONS OF SAID UPPER FRAME WITH AN ANNULAR PIECE OF WIRE CLOTH HELD THEREBETWEEN BY MEANS OF FILLETED SOLDER, SIMULTANEOUSLY EXERTING A DOWNWARDLY AND RADIALLY DIRECTED INWARD FORCE ABOUT SUBSTANTIALLY ALL OF THE PERIPHERY OF THE FLANGE OF THE UPPER FRAME UNIFORMLY TO DEFORM SAID ANGLED FLANGE ON SAID LOWER SKIRT DOWNWARDLY AND RADIALLY OUTWARDLY AND SAID TURNED FLANGE ON SAID UPPER ANNULAR FRAME DOWNWADLY AND RADIALLY INWARDLY ABOUT THE EDGE OF SAID RADIALLY OUTWARDLY DEFORMED FLANGE ON SAID SKIRT TO THEREBY INCREASE THE TENSION ON SAID CLOTH. 